FLEX TEST : Will 37's Clear a JL Rubicon running 2.5" of Lift & Without Rubbing??
There was never any question for Cindy and I that JET Li, our brand new 2018 Jeep JL Wrangler Rubicon Unlimited, would be running a set of 37" tires and much sooner than later. What was in question was, how would we get there? How much lift would it take to clear them and could it be done with wheels that have a bigger amount of back spacing especially now that JL Rubicons come with 68" wide axles? In the end, we decided to run 37x13.50 Cooper STT Pros mounted on KMC XD231 beadlock wheels that have 4.75" of back spacing and try to make it all work with an EVO 2.5" Stage 4 Budget Boost, complete with all 8 adjustable control arms.
Soon after getting everything installed, an initial test drive showed us that this setup worked great or at least, around town anyway. The 2.5" coil spacer lift provided plenty of room to clear the 37" tires and we saw no rubbing at a full lock, in either direction and this in spite of the tires being 13.50 wide and mounted on wheels with 4.75" of back spacing. So, the real question now was, how would this setup do off road? Fortunately, for us, a good flex test was just down the street from us and the following are pics of what we found.
While ramping a Jeep or lifting it from one corner with a forklift can give you an idea of things, the best way to see just how much flex it really has is to get it twisted up. The opposing flex will force the axles to mash into the bump stops and drop the opposite side down to a full droop. Unfortunately for us, we were already hearing a good amount of rubbing well before we could work our way up into our testing obstacle but, here we went anyway. For our first test - driver side front up and turned to the left.
As you can see here, the front jounce stop or bump stop is fully compressed.
In spite of how this pic may look, there is no rubbing of the tire on the driver side fender liner, coil perch, frame rail or other wise that we could see on the driver side and with the wheels turned to the left.
At a full droop, the passenger side coil is still seated properly.
Brake and ABS lines all seem to be good.
Turning to the right to check for any rubbing or clearance issues.
Here you can see that the tires clear the front bumper and grill.
Amazingly, the 13.50 wide Cooper STT Pros tuck up and under the fender as well but then, a lot of this has to do with the 4.75" of back spacing that the KMC XD231's have.
View from the back of the driver side front wheel well to show the fully compressed bump stop and shock.
With the wheels turned, you can get a better look at the passenger side front coil bend.
Moving to the back of our JL Wrangler to get a better look at things.
With the driver side rear tire drooped out, we could see where it had be rubbing a bit on the lower fender liner that covers the bumper.
On the passenger size, we could see that the tire was making full contact with the lower fender liner that covers the bumper.
The bigger problem we found was that the lip of the main fender liner was catching on the tire lugs and getting pulled up. In fact, you can see that a push tab had already gotten pulled out. This was clearly the source of most of what we were hearing.
Looking toward the front of the rear wheel well, we saw that things were clearing well. Certainly, no issues with the pinch seam or rock slider like you would have seen on a JK.
Moving forward through the obstacle so that we can switch our twist.
Verifying that we have full stuff by making sure that the bump stop is fully mashed.
It's close but the back of the passenger side front tire just misses the fender liner when turning to the right.
Turning about half way back to the left, the tread just kisses the fender trim as you can see here. Being that we are at a full stuff, this shouldn't be a problem.
At a full stuff and lock to the left, everything clears and you can see where the tread just kissed the fender trim.
Toward the front of the fender, you can see how the tire is just making contact with it here.
And toward the very front as well.
Like the driver side, the tire clears the grill just fine.
Pushing all the way through the obstacle.
Back on level ground, you can see where the passenger side front tire was brushing up against the fender liner.
Looking back at the passenger side rear wheel well, you can see how mangled the fender liner got.
The driver side rear fender liner fared better but I think it'll just be a matter of time before it gets mangled up too.
And that concludes our first flex test running 37x13.50 Cooper STT Pros mounted on KMC XD231's and all sitting on top of an EVO 2.5" Stage 4 Budget Boost. As you can see, we'll need to head back to the shop and make some modifications.
There was never any question for Cindy and I that JET Li, our brand new 2018 Jeep JL Wrangler Rubicon Unlimited, would be running a set of 37" tires and much sooner than later. What was in question was, how would we get there? How much lift would it take to clear them and could it be done with wheels that have a bigger amount of back spacing especially now that JL Rubicons come with 68" wide axles? In the end, we decided to run 37x13.50 Cooper STT Pros mounted on KMC XD231 beadlock wheels that have 4.75" of back spacing and try to make it all work with an EVO 2.5" Stage 4 Budget Boost, complete with all 8 adjustable control arms.
Soon after getting everything installed, an initial test drive showed us that this setup worked great or at least, around town anyway. The 2.5" coil spacer lift provided plenty of room to clear the 37" tires and we saw no rubbing at a full lock, in either direction and this in spite of the tires being 13.50 wide and mounted on wheels with 4.75" of back spacing. So, the real question now was, how would this setup do off road? Fortunately, for us, a good flex test was just down the street from us and the following are pics of what we found.
While ramping a Jeep or lifting it from one corner with a forklift can give you an idea of things, the best way to see just how much flex it really has is to get it twisted up. The opposing flex will force the axles to mash into the bump stops and drop the opposite side down to a full droop. Unfortunately for us, we were already hearing a good amount of rubbing well before we could work our way up into our testing obstacle but, here we went anyway. For our first test - driver side front up and turned to the left.
As you can see here, the front jounce stop or bump stop is fully compressed.
In spite of how this pic may look, there is no rubbing of the tire on the driver side fender liner, coil perch, frame rail or other wise that we could see on the driver side and with the wheels turned to the left.
At a full droop, the passenger side coil is still seated properly.
Brake and ABS lines all seem to be good.
Turning to the right to check for any rubbing or clearance issues.
Here you can see that the tires clear the front bumper and grill.
Amazingly, the 13.50 wide Cooper STT Pros tuck up and under the fender as well but then, a lot of this has to do with the 4.75" of back spacing that the KMC XD231's have.
View from the back of the driver side front wheel well to show the fully compressed bump stop and shock.
With the wheels turned, you can get a better look at the passenger side front coil bend.
Moving to the back of our JL Wrangler to get a better look at things.
With the driver side rear tire drooped out, we could see where it had be rubbing a bit on the lower fender liner that covers the bumper.
On the passenger size, we could see that the tire was making full contact with the lower fender liner that covers the bumper.
The bigger problem we found was that the lip of the main fender liner was catching on the tire lugs and getting pulled up. In fact, you can see that a push tab had already gotten pulled out. This was clearly the source of most of what we were hearing.
Looking toward the front of the rear wheel well, we saw that things were clearing well. Certainly, no issues with the pinch seam or rock slider like you would have seen on a JK.
Moving forward through the obstacle so that we can switch our twist.
Verifying that we have full stuff by making sure that the bump stop is fully mashed.
It's close but the back of the passenger side front tire just misses the fender liner when turning to the right.
Turning about half way back to the left, the tread just kisses the fender trim as you can see here. Being that we are at a full stuff, this shouldn't be a problem.
At a full stuff and lock to the left, everything clears and you can see where the tread just kissed the fender trim.
Toward the front of the fender, you can see how the tire is just making contact with it here.
And toward the very front as well.
Like the driver side, the tire clears the grill just fine.
Pushing all the way through the obstacle.
Back on level ground, you can see where the passenger side front tire was brushing up against the fender liner.
Looking back at the passenger side rear wheel well, you can see how mangled the fender liner got.
The driver side rear fender liner fared better but I think it'll just be a matter of time before it gets mangled up too.
And that concludes our first flex test running 37x13.50 Cooper STT Pros mounted on KMC XD231's and all sitting on top of an EVO 2.5" Stage 4 Budget Boost. As you can see, we'll need to head back to the shop and make some modifications.
